University students in America have been told not to wear “offensive” halloween costumes including cowboys, indians and anything involving a sombrero.

Students at the University of Colorado Boulder have also been told to avoid “white trash” costumes and anything that portrays a particular culture as “over-sexualised”- which the university says includes dressing up as a geisha or a “squaw” (indigenous woman).

They are also asked not to host parties with offensive themes including those with “ghetto” or “hillbilly” themes or those associated with “crime or sex work.”

In the letter sent by a university official students are asked to consider the impact that their costumes could have.

Christina Gonzales, the dean of students, wrote: “Making the choice to dress up as someone from another culture, either with the intention of being humorous or without the intention of being disrespectful, can lead to inaccurate and hurtful portrayals of other people’s cultures.